Fixed major bugs in report, stairs, plot_heatmap methods.

This release fixes two bugs: 1) NA-only columns number calculation, 2) Y axis labels position on altair heatmap.

This release includes performance optimizations for scikit_na.summary() and scikit_na.stairs() functions.

This update improves the type hints, adds a new function (stairs) and a new type of plot (scikit_na.altair.plot_stairbars).

This release fixes a bug in the report interface with a distribution plot.

First release on GitHub. Includes minor fixes in function signatures.